feat(opencode): session-level model switching API by v1truv1us · Pull Request #22044 · anomalyco/opencode

v1truv1us · 2026-04-11T14:19:56Z

Issue for this PR

Type of change

Bug fix
New feature
Refactor / code improvement
Documentation

What does this PR do?

This adds session-level model persistence so plugins can change the active session model for future turns. The main change is Session.setModel(), plus session storage for model and modelVariant, a PATCH /session/:sessionID/model route, and TUI sync from session state. The chat.message hook remains the integration point for plugins: if a plugin mutates output.message.model, that model is saved on the user message and then persisted onto the session.

How did you verify your code works?

Added targeted tests for Session.setModel() persistence and variant persistence
Verified unknown models are handled without failing the session update
Will rerun the targeted test file after resolving the current merge with upstream/dev

Screenshots / recordings

No UI recording. The UI change is limited to syncing the selected model/variant from persisted session state.

Checklist

I have tested my changes locally
I have not included unrelated changes in this PR

Adds first-class session model switching that allows plugins to dynamically change the active model for a session. Model changes persist across turns, update the UI, and are inherited by subagents. Key changes: - Add model/modelVariant fields to Session.Info with database migration - Add Session.setModel() backend API for programmatic model changes - Add PATCH /session/:sessionID/model HTTP route - Chat.message hook mutations flow through Session.setModel() - TUI syncs session model via reactive effect - Session.fork copies model from original session - Session.create inherits parent model for child sessions - Add adversarial-review plugin example using model routing - Add model-rewrite plugin for env var based model overrides - Remove redundant ModelChanged event (use Event.Updated instead) - Remove dead session.model hook type Tests: 19 new tests for model routing and model-rewrite plugin

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

- Remove hard-coded local plugin path from .opencode/opencode.jsonc - Fix unreachable concurrent session guard in adversarial-review plugin - Fix config load failure message (disabled -> running with defaults) - Add model validation to Session.setModel (logs warning if not found) - Sync modelVariant in TUI session model effect

Remove adversarial-review and model-rewrite example plugins along with related config, specs, tests, and state files. These should live in a dedicated plugins repository.

Merge dev's Effect architecture changes with session model switching feature. Key resolutions: - package.json: take dev's newer dependency versions - session.sql.ts: keep model/model_variant columns, use dev's Permission type - session/index.ts: integrate setModel into Effect layer with model inheritance in create/fork, convert setModel to Effect-based implementation - session/prompt.ts: add model persistence via setModel after user message save in createUserMessage Effect, keep dev's Effect-based insertReminders

Copilot

Pull request overview

Adds a session-level “active model” concept to OpenCode so plugins and clients can switch which provider/model a session uses for future turns, with persistence and a small HTTP/TUI surface area.

Changes:

Persist model + modelVariant on Session.Info (SQLite columns + migration) and expose a Session.setModel() API.
Trigger session model updates after saving a user message when message.model is present (enabling plugin-driven routing via chat.message mutation).
Add PATCH /session/:sessionID/model endpoint and TUI syncing of model changes from session state.

Reviewed changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
packages/opencode/src/session/index.ts	Adds `model`/`modelVariant` to Session mapping + introduces `Session.setModel()` with validation/warn behavior.
packages/opencode/src/session/session.sql.ts	Extends `session` table schema with `model` (json text) and `model_variant` (text).
packages/opencode/migration/20260401004113_add_session_model/migration.sql	Adds SQLite columns for session model + variant.
packages/opencode/migration/20260401004113_add_session_model/snapshot.json	Updates migration snapshot to include the new columns.
packages/opencode/src/session/prompt.ts	After persisting a user message, calls `Session.setModel()` if the message includes a model.
packages/opencode/src/server/routes/session.ts	Adds `PATCH /:sessionID/model` route to update the session’s active model.
packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx	Adds reactive syncing of local model selection from session state changes.
packages/opencode/test/session/set-model.test.ts	Adds tests for persistence and “unknown model” behavior of `Session.setModel()`.

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Copilot · 2026-04-11T14:23:24Z

packages/opencode/src/session/index.ts

 import { Config } from "../config/config"
 import { Flag } from "../flag/flag"
 import { Installation } from "../installation"
+import { Provider } from "../provider/provider"
+import { ModelID, ProviderID } from "../provider/schema"


The new relative imports for Provider/ProviderID/ModelID duplicate existing imports later in this file (via the @/ alias). This will cause TS "duplicate identifier"/conflicting import errors and can also result in two distinct module instances depending on TS path mapping. Remove one set and use a single import path consistently (prefer the existing @/ imports used elsewhere in this file).

Copilot · 2026-04-11T14:23:25Z

packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx

+    const modelKey = `${sessionModel.providerID}/${sessionModel.modelID}/${sessionVariant ?? ""}`
+    if (modelKey === lastSessionModelID) return
+
+    lastSessionModelID = modelKey
+    local.model.set(sessionModel)
+    if (sessionVariant !== undefined && sessionVariant !== null) {
+      local.model.variant.set(sessionVariant)
+    }


When the session model changes to a value with no modelVariant (null/undefined), this effect never clears the local variant, so the UI can keep showing/sending a stale variant from a previous model selection. Update the effect to explicitly clear/reset local.model.variant when sessionVariant is nullish (and consider handling the case where sessionModel becomes undefined if that’s possible).

github-actions · 2026-04-11T14:32:57Z

Thanks for updating your PR! It now meets our contributing guidelines. 👍

v1truv1us · 2026-04-11T19:17:02Z

This is my first real open source contribution, so I hope this is helpful! If there is anything I can do to improve it, please let me know!

John Ferguson and others added 5 commits March 27, 2026 01:59

Update opencode.jsonc to remove hardcoded plugin path

049426a

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

chore: remove example plugins (move to plugins repo)

28f6729

Remove adversarial-review and model-rewrite example plugins along with related config, specs, tests, and state files. These should live in a dedicated plugins repository.

Copilot AI review requested due to automatic review settings April 11, 2026 14:19

github-actions bot added the needs:compliance This means the issue will auto-close after 2 hours. label Apr 11, 2026

Copilot started reviewing on behalf of v1truv1us April 11, 2026 14:20 View session

Copilot AI reviewed Apr 11, 2026

View reviewed changes

github-actions bot removed the needs:compliance This means the issue will auto-close after 2 hours. label Apr 11, 2026

Merge upstream/dev and address session model review feedback

f51bc9e

v1truv1us force-pushed the feat/session-model-switching-v2 branch from 639c78f to f51bc9e Compare April 11, 2026 14:49

fix(opencode): force e2e seed script to exit

d46624f

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feat(opencode): session-level model switching API#22044

feat(opencode): session-level model switching API#22044
v1truv1us wants to merge 7 commits intoanomalyco:devfrom
v1truv1us:feat/session-model-switching-v2

v1truv1us commented Apr 11, 2026 •

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v1truv1us commented Apr 11, 2026 •

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